Cooling systems for heat-treated parts and methods of use

ABSTRACT

Systems and methods for cooling a heat-treated metallic part include a plurality of atomization nozzles disposed on a stage and radially disposed about the part to be cooled; and a fluid in fluid communication with the atomization nozzles. The fluid may gas, liquid, or a combination thereof, e.g., water and gas. During use, the atomization nozzles are generally configured to rapidly cool the thicker sections of the part relative to the thinner section since the thicker sections are generally slower to cool. In some embodiments, the stage can be configured to rotate about the part during cooling. Methods are also disclosed. In one embodiment, the method includes moving a plurality of outlets in a horizontal direction while the heat-treated part is stationary while directing an air and water mixture from the plurality of outlets onto the heat-treated metallic part

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 61/834,094 entitled “Cooling Systems for Heat-Treated Parts and Methods of Use” filed Jun. 12, 2013, which is incorporated by reference.

BACKGROUND

The present disclosure generally relates to systems and methods for cooling heat-treated parts, such as metallic work pieces. More particularly, the present disclosure relates to systems and methods for more controlled cooling heat-treated parts of various geometries and thicknesses.

Certain metallic parts, also known as work pieces, are subjected to severe environmental stresses during use. As an example, certain components of jet aircraft turbines and turbines for power generation, particularly the rotational components, are subjected to extreme centrifugal forces and high thermal stresses during use. Such components also have complex geometries, oftentimes irregular shapes, wherein the thickness varies across the metal component.

The metal parts, usually formed of nickel and titanium superalloys, are commonly heat-treated to improve the strength and wear characteristics of the part, so that they can better withstand the rotational and thermal stresses experienced during use. The heat-treating process usually begins in a furnace, wherein the temperature is set precisely to control growth of specific strengthening microstructures. The alloy properties such as hardness, strength, toughness, ductility, elasticity, and the like of the parts can be determined by the type of microstructure, grain sizes, the heat-treatment temperature, the rate of cooling, the composition of the cooling medium, and the like.

After the alloy part is heated and held above a critical temperature for a predetermined duration, the alloy part must then be cooled. A common method of cooling the heat-treated alloy parts is by immersing the part in a fluid bath. This cooling process is commonly referred to as “quenching.” Quenching of alloy work pieces is conventionally achieved by immersing the part in a liquid coolant, such as water or oil. Immersion of the hot part in the liquid coolant rapidly cools the part at a rate that is either sufficient to maintain certain molecular characteristics of the metal that were acquired in the heat-treatment process, or to obtain certain different molecular characteristics that form during the cooling (quenching) process.

For heat-treated parts having complex shapes and alloys that are strain-rate sensitive, quenching through immersion in a liquid coolant typically does not provide uniform cooling throughout the part. Heat dissipates quickly from thin portions of the part, while thicker portions retain heat for much longer periods. The difference in cooling rates between the surface of the part and the inner portions of the part can result in the creation of varying material properties, varying grain structures, or, in extreme cases, cracks in the work piece. Air quenching as opposed to liquid immersion quenching has the advantage of producing a slower cooling of the part than achieved with a liquid bath quench. However, conventional air quenching methods have only a limited capability in cooling work pieces, because it is difficult to control the air quenching process aside from varying the length of time the heated part remains in the cooling air stream. As such, current air quenching processes are not as effective in providing uniform cooling rates to parts having complex geometries and varying thickness.

Thus, uniform cooling of work pieces having complex sizes and shapes is, at best, extremely difficult using current cooling/quenching techniques. As such, there is a need for systems and methods that enable uniform cooling and formation of the desirable metal grain structures in heat-treated parts having complex shapes and sizes, particularly for the rotational parts found in jet engines and turbine generators.

BRIEF SUMMARY

Disclosed herein are systems and methods for the uniform cooling of a heat-treated alloy part. In one embodiment, a system for cooling a heat-treated metallic part comprises a housing configured to hold the heat-treated metallic part; at least one shroud assembly comprising an array of atomization nozzles configured to be concentrically disposed about the part during operation of the system, each atomization nozzle comprising an outlet; and a fluid source in fluid communication with the plurality of atomization nozzles, wherein the outlet is oriented to discharge atomized fluid at the heat-treated part.

In another embodiment, the system for cooling a heat-treated metallic part, comprises a housing configured to hold the heat-treated metallic part in a stationary position; at least one shroud assembly comprising an array of atomization nozzles configured to be concentrically disposed about the part during operation of the system and configured to discharge a fluid at the heat-treated part, wherein the at least one shroud assembly is configured to oscillate in a horizontal direction about the stationary heat treated metallic part; and a fluid source in fluid communication with the array of atomization nozzles.

A method of cooling a heat-treated metallic part comprises inserting the heat-treated metallic part into a cooling system, the cooling system comprising a housing configured to maintain the heat-treated metallic part in a stationary position; at least one shroud assembly comprising an array of atomization nozzles configured to be concentrically disposed about the heat-treated metallic part during operation of the system; forming an atomized fluid from the atomization nozzle, the atomized fluid consisting essentially of gas and water mixture, wherein the air is at a pressure greater than 0 to 300 psi and the water is at a pressure greater than 0 to 300 psi; and spraying the heat-treated metallic part with the atomized fluid, wherein the atomized fluid consists of atomized droplets.

In another embodiment, the method comprises positioning a plurality of outlets relative to the heat-treated metallic part; and moving a plurality of outlets in a horizontal direction while the heat-treated metallic part is stationary while directing an air and water mixture from the plurality of outlets onto the heat-treated metallic part.

The disclosure may be understood more readily by reference to the following detailed description of the various features of the disclosure and the examples included therein.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Referring now to the figures wherein the like elements are numbered alike:

Figure (“FIG.”) 1 schematically illustrates a turbine disk in accordance with an embodiment of the present disclosure;

FIG. 2 schematically illustrates a perspective view of a cooling system in accordance with the present disclosure, wherein the cooling system utilizes opposing shroud assemblies including arrays of atomization nozzles;

FIG. 3 schematically illustrates an enlarged perspective view of a lower shroud in the cooling system of FIG. 2;

FIG. 4 illustrates an elevational view of a cooling system in accordance with another embodiment of the present disclosure, wherein the cooling system utilizes a single shroud assembly including arrays of atomization nozzles;

FIGS. 5 and 6 illustrate perspective views of the cooling system of FIG. 4 in the lowered and raised positions, respectively; and

FIG. 7 graphically illustrates temperature as a function of time for a part cooled by air only (i.e., convection only) and cooled by an air-water mixture in accordance with the present disclosure.

DETAILED DESCRIPTION

Disclosed herein are systems and methods for the rapid and highly controlled cooling of a heat-treated metallic part. The heat-treated metallic part to be cooled can be any metallic material. In some embodiments, the heat-treated part is a high temperature aerospace alloy. Typically, these materials must have adequate performance characteristics for its intended use, such as tensile strength, creep resistance, oxidation resistance, and corrosion resistance, at high temperatures. More particularly, the systems and methods are configured to maintain highly controlled cooling across the surface of the metallic part being heat-treated by tailoring the heat transfer coefficient in specific areas of the part based on the cross-sectional thickness of the part in those locations. The systems and methods disclosed herein can be particularly advantageous in the production of jet engine and gas turbine generator components, such as turbine disks, and the like.

The production of metallic parts, such as turbine components, generally begins with the shaping of a billet, e.g., an alloy billet in the case of turbine components. The alloy billet is forged into the desired shape under heat and pressure. In order for the shaped part to have the desired microstructure and mechanical properties, the shaped part is then heated and held at a predetermined temperature for a predetermined duration. The part is then cooled in a separate step, commonly referred to as quenching. For most applications, uniform cooling of the heat-treated part is desired because it will promote the development of a uniform grain structure within the alloy composition and minimize distortion of the piece. The cooling method described herein rapidly produces the desired microstructure of the material and desired mechanical properties while avoiding physical defects in the part, such as cracking or distortion that may occur in other systems and processes. Advantageously, the cooling process, also referred to herein as a quenching process, provides a substantially uniform and rapid reduction in temperature.

While the cooling systems and methods disclosed herein can be useful for the rapid and controlled cooling of any heat-treated part, the systems and methods are particularly useful for heat-treated metallic parts intended to be used as components in jet turbine engines and generators. The turbine components, such as turbine disks and casings, are typically circular in shape with radial cross-sections having complex geometries and/or varying thickness across the diameter of the part. In one embodiment, the turbine components are axisymmetric. As such, for ease in discussion, further description of the cooling systems and methods will be with respect to the controlled cooling of a turbine disk. However, it is to be understood that the systems and methods described herein are not limited to turbine disks, but are applicable to any heat-treated part where controlled cooling is highly desirable.

Referring to FIG. 1, a cross-sectional view of an exemplary turbine component is a turbine disc 10 that is representative of a heated treated part to be cooled. The illustrated cross-section of the turbine disk 10 has a complex axisymmetric geometric shape, rather than the simple rectangular shape that would be seen in the cross-section of a plain flat disc. Thus, as used herein, the term complex geometric shape is generally defined as a three dimensional object having varying thicknesses. As shown, the turbine disk 10 is radially symmetrical, i.e., axisymmetric having a radial cross-section that is uniform about the entire circumference of the part. The turbine disk 10 includes an inner portion 12, which forms the disk hub. A second portion 14 of the disk 10 exists between the inner portion 12 and the outer portion 16, which is located about the circumference of the disk. The thickness of the second portion 14 is substantially greater than that of the inner and outer portions 12, 16. The second portion 14 includes a fin or ridge 18 that protrudes outwardly from the main body of the turbine disk 10. As seen from FIG. 1, the turbine disk 10 varies in thickness across the radius of the disk, and in this embodiment generally comprises about three distinct thicknesses. In other embodiments of a turbine disk, the disk could include channels or grooves (not shown) cut inwardly into the part, further altering the thickness profile of the disk. These dissimilar portions will exhibit different cooling rates due the differences in thickness. If the same amount of cooling were applied to the entire disk, the thicker portions would retain heat longer than their thinner counterparts. In other words, the thicker portions, such as defined by the second portion 14 and ridge 18 will retain heat for a longer period and thus take longer to cool than the thinner portions, such as the inner portion 12 and the outer portion 16. These thinner portions are capable of dissipating heat more quickly than the thicker second portion 14 and ridge 18. The cooling systems and methods disclosed herein are able to cool such turbine disks at a substantially more uniform rate than that previously known, despite the disk's complex shape and varying thickness profile. Moreover, relative to other systems and processes, the cooling systems provides a significant reduction in the cooling rate.

Turing now to FIGS. 2-3, there is depicted a cooling system, generally designated by reference numeral 100, in accordance with the present disclosure for substantially uniformly cooling a heat-treated part 102 such as the turbine component shown in FIG. 1. The illustrated cooling system 100 includes a housing generally defined by reference numeral 104 for supporting an upper shroud assembly 140 via guide and actuation rods 106 or like supports. The housing 104 is not limited to any particular shape and generally includes an access for inserting and removing a heat-treated part 102 to be cooled with the cooling system 100. The illustrated housing 104 includes a plurality of vertical 108 and horizontal beams 110 to support at least the upper shroud 140.

The guide and actuation rods 106 are connected to the one or more of the beams 108 and/or 110 of the housing 104 to vertically position the upper shroud 140 relative to the housing 104 such that the upper shroud assembly 140 can be selectively positioned about the part 102 to be treated as may be desired for different applications, i.e., the upper shroud can be raised and lowered as desired.

In some embodiments, the housing 104 may further include a stage 112 for supporting an optional lower shroud 120 via guide and actuation rods 114. Optionally, instead of a stage 112, the guide and actuation rods 114 supporting the lower shroud assembly 140 may be coupled to one or more of the beams 108 and/or 110 of the housing 104 or may be configured as a separate component. The guide and actuation rods 114 effect vertical positioning of the lower shroud 120 relative to the stationary housing 104. In this manner, a selected one or both of the upper and lower shroud assemblies 120, 140, respectively, can be selectively positioned about the part 102 to be cooled as well as be positioned to permit insertion and removal of the part.

In some embodiments, the guide and actuation rods 106, 114 are coupled to an actuator to effect automated movement, e.g., a hydraulic telescopic rod or the like. In some embodiments, a selected one of the lower shroud assembly 120 or the upper shroud assembly 140 is fixedly coupled to the housing 104 and is not configured to move vertically.

A part holder (not shown) such as a cantilevered beam, support surface, or the like can be employed to support the part during cooling. The cantilevered beam or like support can be fixedly attached to the housing or may be separate therefrom. The part holder is generally configured to permit impact of an atomized air-water mixture onto the heat-treated part to be cooled, the mechanics of which be discussed in greater detail below.

As shown more clearly in FIG. 3, the upper and lower shroud assemblies 120, 140, respectively, are each defined by one or more discs 122 that are mounted on or to a table 124. The discs 122 generally include an aperture dimensioned to accommodate a spaced apart relationship with at least a portion of the width of the heat-treated part 102 to be cooled. In embodiments where there is more than one disc, the discs are spaced apart in a stacked arrangement via supports 116 and configured to be concentrically disposed about at least a portion of a part to be cooled. Each disc 122 can have a different aperture to accommodate the diameter of the part to be cooled, wherein the aperture of the disc closest to the part generally has the largest diameter. A plurality of atomization nozzles 126 are disposed on each disc 122 and are collectively referred to as an array. The plurality of atomization nozzles 126 comprise outlets oriented to fluidly cool the part to be treated when the shroud assemblies are in the desired position. The atomization nozzles 126 can be configured to atomize and project a fine spray of droplets onto the heat-treated part to be cooled. The droplet spray pattern can be configured to be substantially repeatable. The number and spacing between adjacent nozzles is not intended to be limited and may be optimized for the intended application. For example, the atomization nozzles may be axisymetrically disposed radially about the disc at equal distances or in some embodiments, the spacing between adjacent atomization nozzles may not be equal.

It should be apparent that atomization nozzles may be supported by means other than a disc. For example, a ring of serially attached atomization nozzles can be used. Alternatively, the atomization nozzles may be disposed on a ring shaped fluid conduit that is in fluid communication with the nozzles and a fluid source.

In the depicted embodiments, the atomization nozzles 126 disposed on the discs 122 are generally configured to space the atomization nozzles 126 from the part 102 at a distance from about 1 to about 24 inches, which may be oriented to spray a fluid onto the heat treated part 102 at an angle that is not normal to the surface. In some embodiments, some or all of the atomization nozzles may spray at an angle that is normal to the surface of the heat-treated part to be cooled. Each array of atomization nozzles 126 within the shroud assembly 120 or 140 can be in a circular pattern that can be axisymmetric around the heat-treated part and oriented to spray inwardly towards the heat-treated part to be cooled. The atomization nozzles 126 are in fluid communication with one or more fluid sources (not shown), which are not intended to be limited. Generally, the fluid sources include at least one gas and at least one liquid. A regulator (not shown) can be employed to control fluid flow for each array. Using air and water as exemplary fluid sources, the system 100 using the atomization nozzles can be configured to selectively spray a fine mist of water in the form of fine droplets upon the surfaces of the part to be treated, wherein the water is gravity fed, lifted via a Venturi effect as is generally well known in the art, or fed via pressurized accumulators or a similar system to achieve required pressures. Air pressures are controlled from greater than 0 to 300 pounds per square inch (psi) and water pressure is controlled from greater than 0 to 300 psi. The fluid can be externally mixed as a mixture or within conduits (i.e., upstream of the nozzle) or internally mixed within the atomization nozzle. In this manner, each part surface that requires a different cooling rate can be sprayed with a set of atomization nozzles whose fluid pressures, e.g., water and air pressure, are tailored to achieve that surface's cooling rate such that the cooling rates are substantially uniform for the different thicknesses. The fluid pressures may be adjusted via the regulator during cooling to adjust a surface's cooling rate as may be desired to provide the intended metallurgical properties. The fluid sources may be contained within vessels (not shown) fluidly connected to the atomization nozzles 126 using a conduit (not shown) or via a manifold (not shown).

Using fluid sources that include at least one gas and at least one liquid is beneficial relative to gas-only or liquid-only cooling. Gas only provides convective cooling that limits the minimal spacing between nozzles to permit egress of the gas after contact with the part surface. With regard to liquid-only quenching systems, liquids are non-compressible and thus functions hydraulically, which limits it practicality. By use of gas-liquid atomization, more effective cooling has been realized in terms of uniformity and efficiency. In one embodiment, an air and water mixture is atomized within the atomization nozzles and sprayed onto the part to be cooled. In one embodiment, the water (or liquid) is fed to the atomization nozzles via a pump, compressed gas, or the like. To minimize pulsing flow such as may occur with the use of pumps that hydraulically deliver the liquid to the atomization nozzles, the liquid can be pressurized using a gas, i.e., gas over liquid delivery, to provide a more constant fluid flow to the atomization nozzles.

Optionally, the table 124 (see FIG. 2) upon which the shroud assemblies 120 or 140 are mounted include a rotatable stage 128 (shown more clearly in FIG. 3 with respect to shroud assembly 120; shroud assembly 140 may be configured to be rotatable in a similar manner). The stage 128 is configured to rotated within a stationary annular ring 130. In this manner, the one or more shroud assemblies 120 and 140 including the arrays of atomization nozzles 126 can be configured to oscillate or rotate in a horizontal plane while the heat-treated part is stationary such as by a hydraulic linear actuator 132, for example, as is partially shown in FIGS. 2-3 or a motorized crank 232 as is generally shown in FIG. 5, or the like to further increase cooling uniformity. That is, during cooling the array of atomization nozzles horizontally rotates about the axis of a stationary heat-treated part to be cooled. The actuator is note intended to be limited and may be mechanical, hydraulic, pneumatic, piezoelectric, electromechanical or any other actuation system intended to oscillate and/or rotate the shroud assemblies relative to the stationary part. It is advantageous to maintain the heat-treated part in a stationary position as to make it less likely for the part to fall and become damaged. Moreover, increased cooling uniformity is provided especially in the situation where one or more nozzles may have failed. The shrouds can independently be configured to rotate or oscillate about its axis during the cooling process. Again, it should be apparent that the rate of oscillation may be unique for each forging.

Optionally, the atomization nozzles can be configured to move vertically during the cooling process. In this optional embodiment, the plurality of atomization nozzles can be selected to articulate or alternatively, the shrouds 120 or 140 upon which the atomization nozzles are disposed, can configured to move in a vertical direction during the cooling process. Thus, oscillation relative to a stationary heat treated part to be cooled can be effected in the horizontal direction, the vertical direction, or both the horizontal and vertical directions as may be desired for some applications.

Turning now to FIG. 4, there is shown a cooling system 200 configured with a single shroud assembly 220 connected to a housing 204. The shroud assembly 220 is similar in construction and function to shroud assemblies 120, 140 as previously discussed. The shroud assembly 220 includes one or more spaced apart discs 222 (or the like), each having thereon an array of atomization nozzles 226. The shroud assembly 220 is generally disposed above a heat-treated part 202 to be cooled and is configured to be selectively raised or lowered via guide and actuation rods 206. However, it should be apparent that the shroud assembly 220, if desired, can be generally disposed below the heat treated part 202 and raised or lowered via guide and actuation rods 206. The heat-treated part is seated on a support 203 such as a stage, cantilevered beam, or the like. Optionally, the one or more spaced apart discs 222 can be disposed onto a rotatable stage as previously described using a motorized crank system 232 or other rotary actuator to effect rotation or oscillation about a horizontal plane during use while the part to be cooled is stationary. FIGS. 5 and 6 depict the shroud assembly of the cooling system in the lowered and raised position, respectively.

In operation of the exemplary cooling system 100, a heated-treated part 102 at an elevated temperature is removed from a furnace and inserted into the cooling system. One or both shroud assemblies 120, 140 are first vertically positioned to accommodate insertion of the heat-treated part and repositioned such that the shroud assemblies 120 and 140 and arrays of atomization nozzles 226 are concentrically disposed about the heat-treated part. A fluid mixture of gas and liquid, e.g., air and water, is then fed to the atomization nozzles, wherein the pressures of the air and water are effective to atomize the water so as to provide fine droplets to about the surface of the heat-treated part, thereby, in the case of an air/water mixture, generating mist. The liquid component of the atomization fluid can be the primary coolant for the cooling system. The spray is continued until a desired temperature is reached, e.g., ambient temperature. In some embodiments, the temperatures of the air and/or water can vary prior to discharge from the atomization nozzles.

The period of time required to cool the forging (i.e., heat-treated part) will generally depend upon the cross-sectional area of the forging. The cooling rate may be constant throughout the cooling process or ramped by adjusting the fluid pressures to the nozzles and/or by selection of the atomization nozzles.

FIG. 7 graphically illustrates a comparison of the cooling process in accordance with the present disclosure relative to an air-only cooling process. In this process, a sample block was heated two times and subsequently cooled by the cooling process in accordance with the present disclosure and the air-only cooling process. As shown, the cooling process was generally non-linear compared to the air-only process and provided a marked reduction in cooling time. Upon additional analysis, it was observed that the mist cooling curve reduced the thermal shock at the onset of the cooling process. Thus, the chances of cracking the part were reduced.

The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A system for cooling a heat-treated metallic part, comprising: a housing configured to hold the heat-treated metallic part; at least one shroud assembly comprising an array of atomization nozzles configured to be concentrically disposed about the part during operation of the system, each atomization nozzle comprising an outlet; and a fluid source in fluid communication with the plurality of atomization nozzles, wherein the outlet is oriented to discharge atomized fluid at the heat-treated part.
 2. The system of claim 1, wherein the heat-treated metallic part is substantially circular in shape with radial cross-sections having complex geometries and varying thickness across a diameter of the part.
 3. The system of claim 1, wherein the heat-treated metallic part is axisymmetric.
 4. The system of claim 1, wherein the fluid source comprises a gas and a liquid.
 5. The system of claim 4, wherein the fluid is configured to provide atomization external to the nozzle
 6. The system of claim 4, wherein the atomization nozzles are configured to provide atomization within the nozzle.
 7. The system of claim 4, wherein the atomization nozzles are configured to provide atomization upstream of the atomization nozzle.
 8. The system of claim 4, wherein the gas is air and the liquid is water.
 9. The system of claim 8, wherein the air is at a pressure of greater than 0 to 300 pounds per square inch (psi) and the water is at a pressure of greater than 0 to 300 psi.
 10. The system of claim 8, wherein the water is pressurized in a vessel by a gas and is in fluid communication with the atomization nozzles.
 11. The system of claim 1, wherein the at least one shroud assembly consists of an upper shroud assembly and a lower shroud assembly.
 12. The system of claim 1, wherein the at least one shroud assembly is configured to be rotatable in a horizontal direction relative to ground during operation, wherein the heat-treated part is stationary.
 13. The system of claim 1, wherein the atomization nozzles are configured to vertically oscillate relative to ground during operation.
 14. The system of claim 12, wherein the atomization nozzles are further configured to vertically oscillate in the vertical direction relative to ground.
 15. The system of claim 1, wherein the at least one shroud assembly is configured to be vertically adjustable relative to ground.
 16. The system of claim 1, wherein the atomization nozzles are radially disposed about the heat treated part at equal distances.
 17. The system of claim 1, wherein the atomization nozzles are at a distance of about 1 to about 24 inches from the heated-treated part during operation.
 18. The system of claim 1, wherein the arrays of atomization nozzles are configured to rapidly cool a thicker section of the heat-treated part relative to a thinner section.
 19. A method of cooling a heat-treated metallic part, comprising: inserting the heat-treated metallic part into a cooling system, the cooling system comprising a housing configured to maintain the heat-treated metallic part in a stationary position; at least one shroud assembly comprising an array of atomization nozzles configured to be concentrically disposed about the heat-treated metallic part during operation of the system; forming an atomized fluid from the atomization nozzle, the atomized fluid consisting essentially of gas and water mixture, wherein the air is at a pressure greater than 0 to 300 psi and the water is at a pressure greater than 0 to 300 psi; and spraying the heat-treated metallic part with the atomized fluid, wherein the atomized fluid consists of atomized droplets.
 20. The method of claim 19, wherein the gas is air.
 21. The method of claim 19, further comprising oscillating the at least one shroud assembly in a horizontal direction about the stationary heat treated metallic part during operation.
 22. The method of claim 19, wherein the at least one shroud assembly consists of an upper shroud assembly and a lower shroud assembly.
 23. The method of claim 19, wherein spraying the heat-treated metallic part with the atomized fluid is a substantially constant cooling rate.
 24. The method of claim 19, wherein spraying the heat-treated metallic part with the atomized fluid is at a ramped cooling rate.
 25. A method of cooling a heat-treated metallic part, comprising: positioning a plurality of outlets relative to the heat-treated metallic part; and moving a plurality of outlets in a horizontal direction while the heat-treated metallic part is stationary while directing an air and water mixture from the plurality of outlets onto the heat-treated metallic part.
 26. The method of claim 25, wherein positioning the plurality of outlets relative to the heat-treated metallic part comprises concentrically positioning the plurality of outlets about the heat-treated part at regularly spaced intervals.
 27. The method of claim 25, wherein the air is at a pressure greater than 0 to 300 psi and the water is at a pressure greater than 0 to 300 psi.
 28. The method of claim 25, wherein the plurality of outlets comprise atomization nozzles.
 29. A system for cooling a heat-treated metallic part, comprising: a housing configured to hold the heat-treated metallic part in a stationary position; at least one shroud assembly comprising an array of atomization nozzles configured to be concentrically disposed about the part during operation of the system and configured to discharge a fluid at the heat-treated part, wherein the at least one shroud assembly is configured to oscillate in a horizontal direction about the stationary heat treated metallic part; and a fluid source in fluid communication with the array of atomization nozzles.
 30. The system of claim 29, wherein the fluid source comprises air and water.
 31. (canceled)
 31. (canceled)
 32. The system of claim 29, wherein the atomization nozzles are configured to articulate in a vertical direction during operation.
 33. The system of claim 29, wherein the at least one shroud assembly is configured to move in a vertical direction.
 34. The system of claim 30, wherein the air is at a pressure of greater than 0 to 300 pounds per square inch (psi) and the water is at a pressure of greater than 0 to 300 psi.
 35. The system of claim 30, wherein the water is pressurized in a vessel by a gas. 